Treating the roots of seedlings, especially tree seedlings such as conifer nursery seedlings, prior to transplanting is a known practice. Usually, the roots of the seedlings are simply dipped into a treatment solution prior to planting the seedling in the desired growth media. Root-soak and root-coat treating solutions have included pesticides, fungicides, microorganisms, and polymeric materials to prevent desiccation. The objective of the treatment is to enhance the survival rate and the re-growth rate of the treated seedlings.
In many cases, the phytotoxicity of a potential treatment material or compound precludes intimate contact between the root and the treatment material as would be encountered in the normal manner of dipping roots into solutions or suspensions of the treatment material. For this reason, typical nitrogen fertilizers, which generally have a sizeable content of readily available nitrogen, have not been routinely used in root treatment compositions. It has been suggested that by pre-coating the roots before treatment even phytotoxic materials can be used in such applications. The complexity introduced by such proposal, however, has prevented general acceptance of this approach.
Fertilizer is often applied as a formulated (N—P—K) solid, granular or powder, or sometimes as a liquid to an area to be fertilized. There are basically two types of fertilizers, water soluble fertilizers and “slow release” fertilizers. While water soluble fertilizers are generally less expensive than slow release fertilizers, they have the disadvantage of leaching nutrients very quickly into and through the soil. Some solid, water soluble fertilizers can be made slow release by various coatings. Alternatively, a reduction in nitrogen availability also can be obtained by using enzyme inhibitors. Slow release fertilizers are designed to release nutrients to plants or soil over an extended period of time, which is more efficient than multiple applications of water soluble fertilizers. Therefore, slow release fertilizers (also referred to as controlled release or extended release) minimize the frequency with which plants must be fertilized, as well as reduce or minimize leaching.
Urea-formaldehyde (UF) condensation products are widely used as slow release nitrogen fertilizers in crops, ornamental plants and grasses. Urea-formaldehyde fertilizer materials also can be supplied either as liquids or as solids and are the reaction products of urea and formaldehyde. Such materials generally contain at least 28% nitrogen, largely in an insoluble but slowly available form.
Extended release UF fertilizers (ureaform) can be prepared by reacting urea and formaldehyde at an elevated temperature in an alkaline solution to produce methylol ureas. The methylol ureas then are acidified to polymerize the methylol ureas to methylene ureas, which increase in chain length as the reaction is allowed to continue.
The methylene urea polymers that the condensation products normally contain have limited water solubility and thus release nitrogen throughout an extended period. The mixture of methylene urea polymers generally have a range of molecular weights and are understood to be degraded slowly by microbial action into water soluble nitrogen. Even so, the commercially available UF fertilizers, which are usually evaluated by the amount and the release characteristics of their water insoluble nitrogen, typically release their nitrogen too rapidly to be useful in seedling treatment applications.
The forestry industry which is responsible for supplying the vast numbers of tree seedlings required annually for re-planting reforestation sites has long desired ways for reducing the incidence of seedling mortality, both in the greenhouse, and after planting at the reforestation site. Compositions which can successfully enhance either the rate at which the nursery-grown seedlings mature, and/or develop during the critical growth stages which follow re-planting of those seedlings in the field, would be a welcome addition to the industry.
The present invention proposes to provide a new source of a particulate slow-release nitrogen (UF) as an economical, non-phytotoxic, biodegradable and environmentally friendly fertilizer treatment composition for seedlings which does not pollute the surrounding soil, and which is relatively inexpensive, and which optionally can effectively function with other nutrient added ingredients if desired, to provide the necessary nutrients, especially nitrogen fertilization, to a seedling.
The term non-phytotoxic refers to the property of a material in not causing plant death or serious plant injury. When used in reference to a treatment for the roots of a seedling, non-phytotoxic means that the material is capable of application to a plant in a manner which does not cause substantial toxicity (e.g., statistically significant reduction in the growth rate of the plant). Such toxicity can be measured, for example, by greenhouse trials comparing the growth of plants with various formulations of the material to controls that are not treated with the material. A material is not phytotoxic if there is no statistically significant toxicity of the material alone, or there is an offset of any significant toxicity by growth-promoting components that can be included in the treatment composition.